Cholesterol is an essential substance in human life activities, and it is a complex similar to fat, mostly produced by the liver. The total amount of cholesterol in the human body is 100-200 grams. 2/3 of them are self synthesized in the body, and 1/3 come from food.
Two important physiological functions.
First, cholesterol is an important component of biofilms, which plays an important role in controlling the fluidity of biofilms. It can also prevent membrane phospholipids in biofilms from becoming crystalline at low temperature, thus ensuring the fluidity and normal function of biofilms at low temperature.
Second, cholesterol synthesizes bile acids and participates in the digestion and absorption of lipids; Synthesis of adrenocortical hormone, androgen and estrogen, with a wide range of physiological effects; It synthesizes vitamin D and participates in calcium and phosphorus metabolism in the body, thus ensuring the normal development and metabolism of bone.
Two main sources
One is from food, the other is synthesized in the body. Human cholesterol is mainly synthesized by the body itself. It can synthesize about 1g every day, and only takes a small amount from food. Cholesterol in normal people’s daily diet mainly comes from animal viscera, egg yolk, cream, meat and other animal foods.
In addition to brain tissue and mature red blood cells, almost all tissues of the body can synthesize cholesterol. The liver is the main place to synthesize cholesterol. 70% – 80% of cholesterol in the human body is synthesized by the liver and 10% by the small intestine.
The main route
Cholesterol in the human body is constantly generated and consumed at the same time, so as to avoid excessive cholesterol accumulation in the body and cause harm. The conversion of cholesterol into bile acids in the liver is the main route of cholesterol metabolism in the body. Normal people synthesize 5g cholesterol every day, of which about 2 / 5 (0.6g) is converted into bile acids in the liver, which are discharged into the intestine with bile to promote the digestion and absorption of lipid substances.
Other pathways of cholesterol consumption include aldosterone, glucocorticoid, androgen and estrogen synthesis in adrenal cortex, androgen synthesis directly from cholesterol in testis, estrogen and progesterone synthesis in ovary and placenta. These hormones are collectively referred to as steroid hormones, and 90% of them are excreted by the kidneys with urine after inactivation of the liver.
Remote control for total cholesterol level and blood lipid level
In adults without coronary heart disease, the ideal serum total cholesterol level is less than 5.2 mmol / L. Low levels of HDL cholesterol (i.e. less than 0.9 mmol / L) are considered to be the main risk factor for coronary heart disease. More and more evidence shows that the reduction of HDL cholesterol will increase the risk of coronary heart disease, and a higher level of HDL cholesterol can protect the population from coronary heart disease, that is, HDL cholesterol more than 1.6 mmol / L is a negative risk factor for coronary heart disease.
Recent studies have shown that no matter whether the serum total cholesterol level is high or low, as long as the HDL cholesterol level is reduced, the risk of cardiovascular disease and cerebrovascular disease will increase.
